After introducing the ground breaking Air Penetrator AP121 computer fan in 2010, SilverStone engineers have created another breakthrough design that further refines the air channeling fan concept. Typical case fans, no matter how quiet when spinning on their own, usually produce clear audible noise when installed as intake case fans. This higher-pitched noise is the result of air turbulence generated between fan blades and the case’s intake grille. The AP123, on the other hand, uses fan blades with three distinct shape and sizes to create uneven airflow. This design may be slightly louder when the fan is spinning on its own, but when installed as a case fan, it is capable of reducing noise frequency by up to 66%.